> Page fault latency wouldn't really cause huge delays at all from an
application
If you're referring to what I said about log writes, this doesn't relate
to page faults. Log lines simply have to be written to disk, and when
the OS determines that it shouldn't (or can't) cache these writes and
return immediately, it becomes a blocking operation, leading to reduced
server performance. I've run extensive tests on this and discussed the
situation with Valve.
> You're always going to have jitter from syscalls, and syscalls are
exactly what is used to generate what 'FPS' says..
Syscall latency is generally not enough to make a server drop from 150
to 100 FPS, as in your initial example. If it does, there's a serious
OS-side performance issue.
> The point I am trying to make here is that with all the info you
provided above, it's still speculation.
By asking that the FPS number be removed from "stats" output, you seem
to be indicating that it is not a valid measure of performance. I don't
believe that is the case.
> Network frames are driven by the timers off of nanosleep, and
gettimeofday is used to step time inside of the engine.
You are correct. strace also indicates this.
> I know this because the engine is based off of quake 3
Half-Life predates the release of quake3. From what Valve has previously
said, the original GoldSrc engine was based off an improved quake and
quake2 engine. Source and Orangebox have a significant amount of changes
from GoldSrc.
But, what I said applies to all of these.
> I am not sure I agree with your statement that FPS is used to measure
serverside performance, I thought it was people's latency to the server
(lower latency means less error prediction)
When I say "purely server-side performance", I am referring to the
performance of the server itself. CPU and memory usage are also metrics
used to measure server-side performance, but are external to the game
and less informative.
Network latency is important as well, but it's not server-side, and a
problem with network latency has different causes and solutions; for
instance, with low server FPS, we might consider upgrading the server
hardware, whereas with a high network latency, we might look at the
client's forwarding path.
-John
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